Data packets transmitted over the Internet are encoded using a variety of signaling and transmission formats. For example, one well-known format for carrying data packets is known as the Internet Protocol (IP). IP data is typically transported over the Internet using a transmission protocol known as the Transmission Control Protocol (TCP). The resulting combination is often referred to as TCP/IP.
As is the case with many popular technologies, TCP/IP has been standardized based on a general consensus amongst a number of industry personnel, thereby making the format suitable for providing interoperability between the various hardware and software entities that make up the Internet.
Among hardware elements, routers play a significant role in receiving TCP/IP data packets and directing individual data packets to their appropriate destinations based on information carried in the header portion of each data packet. The information in the header portion can be used by routers not only for routing data packets but can also used for enforcement of a desired Quality of Service (QoS), for example.
In this context, there is a certain type of header byte that is used for executing various types of QoS services. This header byte has been defined and refined under different versions of the Internet Engineering Task Force (IETF) standards. Specifically, when used in IPv4 (IP version 4) applications, this header byte is often referred to as a Type of Service (TOS) packet header. When used in IPv6 (IP version 6) applications, the header byte may be referred to as a Traffic Class (TC) packet header. However, regardless of the labeling, the individual bits contained in the header byte are used in the same way in both IPv4 and IPv6. Six of the high order bits (bits 0-5) are referred to as belonging to the differentiated services code point (DSCP) field, while the remaining two low order bits (bits 6 and 7) are either left unused or sometimes used for explicit congestion notification (ECN) purposes.
The DSCP field can be used for conveying QoS related information to one or more routers for purposes of carrying out tasks such as managing traffic congestion queues. As a part of this activity, a router can, for example, utilize the DSCP field to identify and provide precedence to certain types of data packets while dropping certain other types of data packets.
Naturally, in order to effectively interoperate with each other, a first router manufactured by a first manufacturer should recognize and interpret the DSCP field in the same manner as a second router manufactured by a different manufacturer. Therefore, it is in the best interests of the various manufacturers and network operators to comply with standards such as IPv4 and IPv6, even if some of these standards may be less than ideal for their individual needs.
On the other hand, where compliance to these standards is optional, such as in privately owned networks or in dedicated networks, it may be more desirable to use customized solutions for implementing QoS rather than abide by the one-size-fits-all approach.